Carpet and upholstery cleaning equipment has been known and used for many years. Prior to the introduction into the marketplace of a device in accordance with the present invention, the cleaning liquid, i.e. detergent or soap containing water, was merely introduced into a vat or holding tank of the machinery in question, and the cleaning liquid was heated by the use of a simple immersion heater. This type of system, however, provided many problems, some of these being briefly outlined below.
Thus, there is some danger in the use of immersion heaters, e.g. workers can be burned if immersion heaters are not properly handled. In addition, because the cleaning liquid comes in direct contact with exposed heater coils in an open vat, such immersion heaters can only be used when the cleaning liquid is water, i.e. they cannot be used with dry cleaning fluid. Moreover, such immersion heaters work very slowly, requiring approximately 20 minutes to heat 10 gallons of water to about 150.degree. F., or 30-40 minutes to heat 20 gallons of water to the same temperature; this slow operation is required to be repeated each time the cleaning tank is re-filled with water.